Wayside station line coupling means for train communication systems



Nov. 28, 1950 E w BRElsci-l ETAL 25319498 WAYSIDE'STA-TION LINE COUPLINGMEANS FOR TRAIN COMMUNICATION SYSTEMS Filed Feb. 20. 1947 P2 E 5MM? y 1.www

Patented Nov. 28, 1950 WAYSIDE STATION LINE COUPLING MEANS FOR TRAINCOMMUNCATION SYSTEMS Edgar W. Breisch, Edgewood, Robert G. Reed,Swissvale, and Lawrence R. Golladay, Forest Hills, Pa., assignors to TheUnion Switch and Signal Company, Swissvale, Pa., a corporation ofPennsylvania Application February 20, 194.7, Serial No. 729,680

3 Claims.

Our invention relates to wayside station line coupling means for traincommunication systems, and more particularly to such line coupling meansfor inductive carrier communication systems for railway trains.

Inductive carrier communication systems for railway trains make use of atransmitting channel that includes conductors and line wires parallel tothe track. The existing line wires strung on the pole line extendingalong the railway and used for telegraph and similar circuits become apart of the transmitting channel for such inductive carriercommunication system due to the distributed capacitance of the linewires to ground and to their distributed mutual inductance to the trackrails. This use of the line wires in a communication system is inaddition to and without interference with their present use. That is,the longitudinal circuit formed` by line wires due to their distributedcapacitance to ground are elements of a channel with which circuitelements mounted on a train have inductive relation and energy can beinductively transferred between the wayside transmitting channel and thetrain.

These inductive carrier communication systems for railway trainsgenerally provide telephone communication between wayside stations andthe trains as well as between two vehicles of a train or between twodiiierent trains, and

in providing communication between a WaysideA station and trains thestation telephone equipment is generally coupled to the transmittingchannel by being coupled to the longitudinal circuit of line wiresextending along the railway. These train communication systems areusually of the simplex type in which the receiver is normally activeready to receive a telephone call or message and the transmitter isnormally deenerg'ized and is energized and made active only during thesending of a message.

Furthermore, such systems frequently provide two or more carrierfrequency channels on each of which a two-way communication may becarried on, such a multiple channel system permitting a number of trainsto use the system at the same time. A plurality of frequency channelsalso make it possible to provide a break-in feature by which a thirdparty can break in'on a conversation in case emergency train orders needto be transmitted without delay.

Again, the energy level of the transmitter of inductive carriercommunication systems for railway trains is made relatively high becauseof the high attenuation of the current in the trans-- mitting channeland in the relatively long air gap between the transmitting channel andthe train carried elements. For the same reason, relatively high gainreceivers are required. Due to the high energy level of the transmitter,some arrangement must be provided to assure that the output of atransmitter of a station does not swamp the input of the receiver at thesame station. It is common practice to desensitize the local receiverduring sending periods by removal of the anode voltage of one or moreelectron tubes of the intermediate stages of the receiver, but the inputof the first stage of the receiver remains closed. This condition of therst stage of the receiver may result in the input circuits being chargeddue to the high energy level of the local transmitter and such chargeson the receiver input must be dissipated before the receiver canfunction at its normal sensitivity.

In view of the foregoing requisites for inductive train communicationsystems for railway trains, arnain object of our invention is theprovision of improved means for coupling the telephone equipment of awayside station of an inductive carrier communication system for railwaytrains to line Wires.

A feature of our invention is the provision of novel coupling means forconnecting a wayside station transmitter and receiver of a multiplechannel inductive communication system to diierent line wiresparalleling the railway.

Other features, objects and advantages-oi our invention will appear asthe specication progresses.

The foregoing objects, features and advantages of our invention areattained by the provision of a novel circuit network for connecting thetransmitter output and the input of each receiver of a Wayside telephoneequipment to individual pairs of line wires.

For a better understanding of our invention, reference may be had to theaccompanying drawing, which is a diagrammatic view showing one form ofapparatus embodying our invention when used with a two frequency channelinductive carrier communication system for railway trains.

It is to be understood that the invention is not limited-to a twofrequency channel system and this application illustrates the manyplaces the apparatus is useful.

Referring to the drawing, the reference character RT designates a trackof4 a railway which is provided with an inductive carrier communicationsystem. The railway may be a single track road, or it may be a multipleroad of which the track RT is one track. The inductive carrier systemmay take different forms and may be similar to the two frequency channelsystem disclosed in an application for Letters Patent of the UnitedStates Serial No. 575,311, iiled January 30, 1945, by Paul N. Bcssart,for Railway Train Communication and Alarm System Using Modulated CarrierCurrents, now Patent No. 2,484,680, issued October 11, 1949, or it maybe similar tothe apparatus disclosed in Letters Patent of the UnitedStates No. 2,064,639, granted December 15, 1936, to Leland D. Whitelocket al., for Cornmunication Systems. Y

A train is indicated conventionally at TN and a dot and dash rectangleWS indicates a wayside station of the railway. Both the train and thestation are provided with telephone equipment of the train communicationsystem so that an operator at the station WS can communicate with trainTN while it is moving over the track RT. The telephone equipments of thestation and train would be similar and they are shown as being oi thetwo channel arrangement disclosed in the aforementioned Bossartapplication and each equipment comprises two receivers shownconventionally by the reference characters BEER and llR and atransmitter disclcsed 'conventionally by the reference character Sil-IMT.

It is suicient for the present application to point out that thereceiver BSR includes an amplifier, a demodulator and a telephonereceiver for reproducing the voice frequencies of a frequency modulatedcurrent having a carrier frequency of the order of, say 80 kc.Similarly, the receiver UMR includes an amplier, a demodulator and atelephone receiver to reproduce the voice frequencies of a frequencymodulated carrier .current of a carrier of the order of, say 144 kc.These two carriers, 80 kc. and 144 kc., constitute a first and a secondfrequency channel, respectively, for the train communication system. Thetransmitter 23S-IMT includes a modulator, an oscillator and a poweramplier to supply a frequency modulated carrier telephone current ofeither the two channel frequency S kc. or 144 kc. It is to be understoodthat the invention is not limited to these carrier frequencies and otherfrequencies can be used.

On the train TN the receivers SUR and UMR are connected to pick-up coilsPl and P2, respectively, which are mounted on the train to haveinductive relation with a wayside transmitting channel that includes theline wires and other conductors extending along the railway parallel tothe track. The train transmitter Sil-HMT is connected to a sending loopcircuit which as here shown includes two spaced pairs of wheels 3Q and3i o1 ne train and the track rails between these pairs of wheels, andwhich sending loop circuit is arranged for inductive relationship to thewayside transmitting channel. The coupling of the station receivers andtransmitter of the telephone equipment to the transmitting channel willappear shortly.

The reference characters Ll to LB,-inclusive designate line wires whichextend along the railway. Ordinarily, the line wires LI to L would beexistingline wires strung on the usual pole line along the railwayright-of-way so that the wires are approximately parallel to andreasonably close to the track RT. In the drawing only a short portion ofeach line wire is illustrated for the sake of simplicity, but it is tobe understood that these line wires would extend for substantially thefull length of the track equipment for train communication. These linewires Ll to LB would be those usually used for tele-graph, signal andsimilar purposes, and as shown the line wires Ll and L2 are indicated asa pair forming a rst transverse line circuit, line wires L3 and L4 areindicated as a pair forming a second transverse line circuit, and linewires L5 and L@ as forming a third transverse line circuit.

As explained herein, each of these line wires Ll to L5 is a part of atransmitting channel oi the train communication system due to thedistributed capacitance of the line wires to ground and theirdistributed inductance to the rails oi the track. In other werds, thelongitudinal circuit formed by each line wire, or better still, the1ongitudinal circuit formed by each pair of line wires in multiple, is apart of the transmitting channel of the train communication system, andwith which transmitting channel the train carried circuits are mountedfor inductive relation so that energy of the train communication systemis effectively transmitted between the train and points remote from thetrain.

To provide twoway communication between the station WS and train TN, thetelephone equipment at the station is coupled to the line wires. Thiscoupling means includes a coupling unit indicated as a whole by a dottedrectangle Cil and by which coupling unit the transmitter and receiversof the station equipment are connected to the line wires in a novelmanner. The coupling unit CU is provided with two rows of terminals l to6, inclusive, and 'i to i2, inclusive, the terminals being arranged inpairs as will be apparent from an inspection of the drawing. A capacitoris connected between the terminals of each pair. For example, acapacitor C'i is connected between the pair of terminals l and l. Theunit CU also includes an output transformer Tl which is provided with aprimary winding i3 connected to the output of a transmittel` QQ- liT andwith a secondary winding ill connected between the line wires Li and L2and a ground electrode l5. To be specific, the lower terminal ofsecondary winding ifi as viewed in tl e drawing, is connected to theground electrode l5 and the top terminal of secondary windingl it isconnected to the line wire Li through terminal 8, connector i6 betweenterminals T and 8, capacitor Cl, terminal l and wire Il; and isconnected to line wire L2 through terminal 8, capacitor C2, terminal 2and wire i8. That is, the output of the transmitter is coupled to thelongitudinal circuit formed by the two line wires Ll and L2 of the firsttransverse line circuit. 'Preferably the secondary winding iii isprovided with intermediate terminals to permit impedance matching of thetransmitter output with the line circuit.

The input of receiver UMR is coupled to the longitudinal circuit formedby the line wires L3 and L4, through an input transformer T2 and thecoupling unit CU. Transformer T2 is provided with a secondary winding 24connected to the input of the receiver UMR and with a primary winding i9having one terminal connected to a ground electrode 23 and its otherterminal connected to the line wires L3 and L4 in multiple, one path ofthe connection including wire 2|, connection between terminals 9 and ID,capacitor C3, terminal 3 and wire 22 connected to line wire L3; and theother path including wire 2l, terminal I0, capacitor C4, terminal l andwire 23 connected to line wire L4. Similarly, the receiver BUR iscoupled to the longitudinal circuit formed.

path including wire 2l, terminal I2, capacitor C6,l

terminal 6 and wire 29 connected to line wire L6.

It follows that communication current transferred from the train carriedtransmitter to the Wayside transmitting channel will be applied to theinputs of the two receivers 8R and INR at the station WS, due to thecoupling of the receivers to the line wires, the receiver 80B, beingeffectively responsive when the communication current is of the 80 kc.channel and the receiver INR being eiectively responsive when thecommunication current is of the 144 kc. channel. Furthermore, when thewayside station transmitter is made active to supply current of eitherthe 80 kc. channel or of the 144 kc. channel to the transmitting channelalong the railway` the train carried receivers will be selectvelyresponsive to this current due to their coupling to the transmittingchannel.

As explained in the aforementioned Bossart application, the telephoneequipment is arranged so that when the transmitter of the waysidestation is conditioned for sending on the 80 kc. channel, the receiverIMR remains active but the 80B receiver is desensitized by the openingof the anode circuits of electron tubes used in that receiver. Also,when thetransmitter is conditioned to send on the 144 kc. channel, thereceiver'R remains act-ive but the MAR. receiver is desensitized byopening the anode circuits of electron tubes used in that receiver. Ineither case, the input of the iirst stage of each receiver remainsclosed. With the coupling network here provided it is clear that whenthe transmitter of the wayside station is sending on the 80 kc. channel,the electromotive force applied to the input of the local receiver 80H.is only that created on the line wires L3 and L4 due to the distributedinductance of these line wires to the longitudinal circuit formed by theline wires Li and L2- and this electromotive force will be relativelylow compared to the output voltage of the transmitter which would beapplied to the receiver were both the transmitter and receiver coupledto the same pair of line wires as has been the practice heretofore.Also, the electromotive force of the 80 kc. channel applied to thereceiver EMR is relatively low when the transmitter is sending on the 80kc. channel and a relatively simple lter arrangement can be used,whereas if the UMR receiver were coupled to the same line wires as thetransmitter, arrangements must be provided` so that the relatively highenergy level of the output of the transmitter does not swamp the inputof the active receiver. Again, when the transmitter is sending on the144 kc. channel, the electromotive force applied to the ,input of theMdR receiver is relatively low and only that created on the line wiresL5 and L6 due to their distributed inductance and capacitance to thelongitudinal circuit formed by the line wires Ll and L2. Also, theelectromotive force applied to the active receiver 80R due to the eenergy supplied by the transmitter at this time would be relatively low.

It is pointed out that in the case only four line wires are availablethen the input of each receiver would be preferably coupled to one wireof a pair of the line wires while the transmitter is coupled to thesecond pair of the line wires.

We have found that the coupling network here Y.

provided greatly improves communication between a wayside station andtrains. the noise to signal ratio is greatly reduced and minimized wheneach receiver is coupled to both wires of the same pair of line wires.

Line coupling means such as here provided has the advantages that it isof compact design so that it can be mounted to permit any suitablelocation of the wayside station apparatus and in a location mostconvenient for the line wire connection. The adjustable secondary of theoutput permits suiiicient impedance matching of the standard transmitterto the line wires of any existing telephone or telegraph line circuit.High voltage coupling capacitors are an integral part of the couplingunit, and the cou-` pling means can be arranged to take advantage oftelephone line transposition characteristics.

Although we have herein shown and described but one form of waysidestation line coupling means for train communication systems embody- :ingour invention, it is understood that various changes and modications maybe made therein within the scope of the appended claims withoutdeparting from the spirit and scope of our invention.

Having thus described our invention, what we claimis:

1. In a simplex inductive carrier railway train communication systemwhich uses the existing line wires strung on the usual pole line along arailway right-of-way as a transmitting channel due to the distributedimpedance of the line wires to ground and the dstributed mutualinductance of the line wires and to which channel train carried circuitelements are mounted for inductive relation thereto, the combinationcomprising, a transmitter and a receiver of carrier communicationcurrent located at a given wayside station, a plurality of parallelingline wires which form for their entire length a transmitting channel forcarrier current due to the distributed impedance of the separate linewires to ground and due to the distributed mutual inductance of the linewires because of their parallel relationship, an output and an inputtransformer each of which is provided with a primary and a secondarywinding, said primary winding of said output transformer connected tosaid transmitter and said secondary winding of said input transformerconnected to said receiver, a rst circuit including said secondarywinding of said output transformer and a blocking capacitor in seriesconnected between a selected one of said plurality of line wires andground, and a second circuit including said primary winding of saidinput transiormer and another blocking capacitor in series connectedbetween a diierent selected one of said plurality of line wires andground.

2. In a two-way inductive carrier railway train communication systemwhich uses the existing y Also, that4 forming a transverse line circuit,the combina* tion comprising, carrier communication current equipmentincluding `transmitting apparatus and receiving apparatus and located ata given Wayside station, said transmitting apparatus including vacarrier transmitter and an output transformer, said receiving vapparatusincluding a carrier yreceiver and an input transformer, each of saidtransformers provided with a primary and a secondary winding, saidprimary winding of said output transformer being connected to saidtransmitter, said secondary winding of said input transformer beingconnected to said receiver, a plurality of pairs of line Wires, saidline Wires having a parallel relationship and forming for their entirelength a transmitting channel for carrier current due to therdistributed impedance to ground and their distributed mutual inductanceas provided by their parallel relationship, a rst pair of capacitors inseries connected across a first selected pair of said plurality of pairsof Wires, said secondary winding of said output transformer connectedbetween the junction terminal of said rst pair of capacitors and ground,a second pair of capacitors in series connected across a second selectedpair of said plurality of pairs of wires, and said primary winding ofsaid input transformer connected between the junction terminal of saidsecondv pair of capacitors and ground.

3. In combination, a railway track, a plurality of paralleling linewires extending along said track and forming a transmitting channel forcarrier communication current due to their distributed impedance toground and their distributed inductance with each other, a train carriedcommunication equipment having circuit elements mounted for inductivekrelation with said line wires, a wayside communication equipmentincluding a carrier transmitter and a carrier receiver of carriercommunication current and 1ocated along said track and having an.output-andan input transformer each of which is provided with a primaryand a secondary winding, said primary Winding of said output transformerconnected to said transmitter to be supplied with communication current,said secondary windingv iior transmission of communication current fromthe train carried equipment to the wayside equipment due to saidtransmitting channel.

EDGAR W. BREISCH. ROBERT G. REED. LAWRENCE R. GOLLADAY.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,683,716 Espenchied Sept. 11,1928 1,815,976 Green July 28, 1931 2,064,641 Bossart Dec. 15, 19362,064,642 Bossart Dec. 15, 1936 2,124,450 Shaver July 19, 1938 2,240,676Shaver May 6, 1941 2,310,060 Booth Feb. 2, 1943 2,310,097 Langguth et alFeb. 2, 1943 2,393,291 Clark Jan. 22, 1946

